As used herein the term “PV module” identifies a photovoltaic power generating unit in the form of an integrated structure comprising a plurality of electrically interconnected photovoltaic cells and means for supporting and protecting the cells. A variety of systems and methods have been devised for mounting PV modules and associated components of solar electric (PV) power generating systems on the rooftops of businesses, factories, schools, hospitals, commercial establishments and the like, and the market for such systems is growing rapidly in the United States and elsewhere. As the cost per watt has dropped in recent years for photovoltaic units, the need for improving methods of mounting photovoltaic modules to building roofs has become more critical. More precisely, as the cost of solar cells per se has declined, the non-solar cell components required for installing a functioning photovoltaic system become more critical with respect to overall system costs. However, care must be taken to insure that photovoltaic systems are installed with due respect to environmental factors such as wind-loading and environmental stresses, and preserving building integrity, notably, avoiding the use of mechanical fasteners that penetrate the roof covering.
My copending application Ser. No. 10/506,145, cited supra, discloses a system for mounting PV modules on a flat building roof that (1) is adapted to mount PV modules at a selected tilt angle, e.g., in the range of 0°-15°, to benefit annual energy production, (2) allows the PV modules to shift from a tilt position to a near horizontal position in response to pressure differentials caused by extreme winds, whereby to release wind pressure and reduce or substantially eliminate wind uplift forces, (3) eliminates the need for mechanically or adhesively attaching the module-mounting structure to the building roof, whereby to preserve the integrity and waterproof characteristics of the supporting roof structure, and (4) provides for walkways between rows of solar modules for easy access for servicing and repair.
The mounting system disclosed in my above-identified copending application utilizes a plurality of mounting stands that are intended to rest on a supporting roof, with each mounting stand consisting of a base plate, and first and second brackets attached to opposite ends of the base plate. These mounting stands are distributed in spaced relation to one another on a supporting roof in a row and column arrangement. The first bracket has a fixed height and the second bracket has a telescoping construction that permits its effective height to vary from a first minimum value that is less than that of the first bracket to a second maximum value that is substantially the same as the first bracket. Each bracket has dual members for supporting two PV modules. The PV modules are rectangular and are supported by attaching mounting studs located adjacent to each corner of each module to different mounting brackets. More specifically, two corners of each module are mounted to different first brackets and the other two corners of each module are attached to different second brackets. The distributed mounting stands and the supported PV modules provide sufficient weight to resist movement by wind uplift forces resulting from wind velocities of up to about 70 miles per hour. Under higher velocity winds, e.g., winds up to about 110 miles per hour, the ability of the mounting stands and the supported PV modules to withstand movement is enhanced and preserved by the ability of the second brackets to extend their heights so as to shift the modules to a near horizontal position, thereby releasing wind pressure on the modules and reducing wind uplift forces.
Experience has revealed that sometimes the telescoping second brackets tend to bind instead of telescoping readily as designed, restricting the ability of the mounted PV modules to shift to near horizontal position and thereby reduce module-distorting forces caused by wind pressure. The binding problem is related to quality control in the manufacture of the telescoping brackets, and may be worsened by bracket misalignment. It has been observed also that installers sometimes get confused and install the smaller telescoping brackets in reverse. Such error is troublesome since the first and second brackets each have horizontally elongated slots for receiving mounting studs that protrude from opposite sides of the modules, and reversing the telescoping brackets, for example, makes it possible for the modules' mounting studs to slip out of the elongated slots and/or allows the modules to shift in such a way as to prevent them from pivoting upwardly as required when subjected to uplifting wind forces.